This thesis consists of three chapters that can be logically divided into two parts. The first part (1. and 2. chapter) sets out the theoretical basis and properties of deductive databases and Datalog language. Understanding the concepts and results described in the first part is crucial for the realization of deductive database described in the second part of the thesis. Deductive databases were created as a hybrid of logic programming and relational databases, so it is clear that the first-order logic will play a key role in the formalization, development and implementation of deductive databases. First chapter presents some important concepts and results of first-order logic. First we start from the syntax of first-order logic, where we define what do syntactically correct formula of first-order logic language look like. Once we have syntactically correct statements we want to interpret them from the semantic point of view. At the end of the first chapter we introduce some key concepts (Herbrand universe, Herbrand base, Herbrand interpretation) to prepare the way for the second chapter where we define a deductive system for evaluating Datalog programs. The second chapter begins by studying the syntax of Datalog language where we define what do facts and rules by which we store data and derive new knowledge look like. Then we define what does a correctly written Datalog program look like by introducing the concept of stratification. Once we learn how to write Datalog programs correctly we deal with the semantics of Datalog. Here we’ll see how to evaluate Datalog programs using fixed-point iteration as a deductive system, where with the given axioms provided by Datalog program the only deduction rule will be the so-called elementary production. Then we will enable the implementation of Datalog concepts within the relational algebra by mapping a Datalog program into relational algebra. In the second part of the second chapter we aim to improve evaluation of a Datalog program, by studying various evaluation and optimization methods. In the third chapter by using the software that recognizes Datalog language (Logic Query Language) we aim to build a concrete deductive database. The goal is to describe the various capabilities of the software by writing recursive queries over the deductive database.